Non-removable screw.



W. S. FORBES.- NON-REMOVABLE SCREW. APPLICATION FILED FEB.27.1913.

PatentedApr. 9,1918.

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. 7h??? 3251 Howe Witmaooeoz 9g m WALTER SCOTT'FORBEKOF NEW YORK, N. Y.

NoN-Rumovnnnn SCREW.

Specification of Letters Patent.

Patented Apr. 9, 1918.

Application filed February 27, 1913. lSerial No. 751,141.

To all w wmz't may Concern Be it known that I, WALTER S. FORBES, a citizen of the United States, and resident of the borough of'Richmond, 'county of Richmond, city and State of New York, have vinvented certain new and useful Improvements in Non-Removable Screws, of which the following is a specification.

I have found that it is sometimes desirable to set an ordinary wood or machine screw in such a manner that it cannot be readily withdrawn or so that it cannot be withdrawn at all by any ordinary or easily accessible means.

I have found that where a hinge or lock must be placed upon the exterior of a door, gate, or cover and where it is desirable or necessary because of the surrounding conditions to attach said hinge or lock by means of hand or machine driven screws, that could such screws be so constructed that they could not be withdrawn additionalsecurity would result and constructions would be possible that under ordinary conditions are impossible or impractical.

This device is intended kto operate in the manner as above set forth and provides a screw fulfilling these necessary requirements. The means by which this screw is inserted are to be removed when the screw is in place. The construction and operation that accomplishes these very desirable results will be set forth as the specification progresses.

The following is what I consider the best means of carrying out this invention. K

The accompanying drawings form a part of this specification in which Figure l shows my completed device and is in elevation.

Fig. 2 shows a machine screw having certain of my improvements.

Fig. 3 shows a section of the line 3-3'in Fig. l and viewed in the direction of the arrows.

Fig. 4 shows in plana head as it will be constructed for particular heavy duty and large screws.

Fig. 5 shows in plan the head as it will be constructed for ordinary'service.

Fig. 6 shows in plan a hinge or plate with the screw inserted.

Fig. 7 shows a modification in the shape of the screw.

Similar reference numerals indicate like parts in all the figures'where they appear.

The body f an ordinary screw is shown at l, this body is provided with ordinary screw-threads and requires no further description as this construction is not changed or modified in myy device. At 2, I have shown a tapered head of familiar outline.

This head is similar in shape to the ordinary tapered head but the slot usually provided in the upper plane surface is omitted.

Arranged upon the head and spaced definite distances apart I provide a plurality of lugs 3 and 4. These lugs may be of any desirable length or width but for convenience it is my intention that between them they will present projections having just sufficient strength and area to allow the screw to be turned reliably into place.

Between the head and the body of the screw I produce a shank and formed integral with this shank I arrange a plurality of projections 6. I produce these projec-V tions in such a manner that their Hat face shall not retard or make difficult the turning of the screw during the insertion thereof. I may produce but one or two of these projections or I may produce a plurality as shown.

Vhen the screw is used under eXtreme conditions or `when a particularly large screw is to be used I may provide more of the projections 3 and 4 as shown in Fig. 4 and indicated by 7 and 8.

My improved screw may be used in a very ordinary manner the point being started, the blade of the screw driver is placed between the projections 3 and 4, and the screw turned in toits full extent. When all is tight and secure the blade of the screw driver is removed and then with the assistance of a small saw or chisel the projections 3 and 4, useful in setting the screw are removed.

The screw-head will upon the removel of the lugs or projections 3 and 4 present a flat and plain surface, flush with the hinge or plate through which it passes. f

From Fig. 7 it will be seen that these projections may be formed on a. screw of any general shape or construction.

It is my intention that the projections 6 formed in the shank of the screw shall act as teeth oiering no or little resistance while screw is being inserted, but cutting well into the surrounding wood or metal when an attempt is made to withdraw the screw. These teeth or projections may however be omit- 

